The present invention relates to data communications between computer based stations in a network and more particularly to data communications between computer-based stations in a network wherein data is selectively compressed and decompressed to improve network utilization and efficiency.
1. Prior Art
In some network systems, network data bandwidth requirements may increase during busy periods of the day. In many respects, the requirement for data bandwidth varies over the period of a day in a manner similar to the requirement for electric power which varies from peak hours during the daytime to relatively low demand during the early morning hours.
If all the data transmitted across a network are compressed by a predetermined ratio such as two to one, the effective bandwidth of the network is approximately doubled. Using data compression is a much more cost effective and efficient solution to the bandwidth requirement problem than upgrading the network to a faster data rate which would require replacement of very expensive hardware in the system.
Also, employing a compression technique which is hardware based requires new network adapter card designs. This also results in a higher cost.
A software-based compression could use existing adapter cards, but software-based compression requires a large number of system processor cycles which is wasteful when compression is not required, for example, when network utilization is low.
An article in the IBM Technical Disclosure Bulletin, Volume 35, Number 6, published November 1992, at page 394 entitled "Time-based Compression Selection Line Detector Methodology" describes a technique for periodically polling network activity and comparing data transfer time to the time required to compress the same block of data. The technique described in the article is intrusive in that it sends a frame into the network to discover buffer transfer times. This limits the responsiveness of the system and contributes to network and target station load. Contributing to network load during times of high network activity is not a good way to improve network responsiveness. Further, the technique described in the article does not measure network utilization. There are various other reasons than high network utilization that may cause a timed poll to take a "long time." For example, if the target station is busy, the timed poll may indicate a busy network, and the implementation of data compression may actually degrade system performance. Also, the technique measures samples which may yield an inaccurate representation of the average utilization over the sampling period since the sampling period is so long, the recommendation being ten minutes.
The article does not teach nor suggest a dynamic system for efficient data transfer in which data is automatically compressed when network activity exceeds a predetermined threshold.